I've read a forum that explain how to do it

https://www.odoo.com/fr_FR/forum/aide-1/question/show-the-product-availability-on-the-web-74965

The problem is that with thi option I can only display the total quantity availability of the product, not of each product variant. So for example, if the parent product has 10 units in total, children A has 3, children B has 4 and children C has 3. I want to display the children quantities, not the 10 units in total.

Thanks!